Exciplexes are intermolecularly bound excited states of complexes with dissociative or only very weakly bound ground states. A very large class of systems can be classified as excited complexes or "exciplexes." The rare gas halides are singled out for the present application. The rare gas halide exciplexes are charge transfer complexes of rare gas atoms, to be designated by the symbol Rg hereafter, and halogen atoms, to be designated by X hereafter.
The prior art relating to exciplex lasers deals exclusively with gas phase lasers, and primarily with gas phase lasers that are electrically pumped (electron beams or electric discharges). Although high power performance is obtainable with present gas phase exciplex lasers of the type described by the Hutchinson U.S. Pat. No. 4,292,603 entitled "Exciplex Lasers" and in the Sze U.S. Pat. No. 4,301,425 entitled "XECL Avalanche Discharge Laser employing AR as a Diluent," there are significant limitations in some photodynamical parameters. Among the limitations in present gas phase exciplex lasers are: (1) the range of output wavelengths; (2) inefficiencies induced by collisional quenching of the upper laser state; (3) inefficiencies induced by parasitic absorptions in electrically discharged systems, which is the common mode of excitation; (4) relatively small gain coefficients due to the low number densities of exciplexes; and (5) the discrete nature of laser wavelengths and the virtual lack of tunability.
At present, dye lasers are the only broadly tunable coherent radiation sources. Dye lasers consist of a cell containing a dye molecule dissolved in an appropriate solvent. Laser action is induced by pumping the system with a powerful radiation source such as a flashlamp or another laser (quite commonly a gas phase exciplex laser). Dye lasers operate in the 320-950 nm spectral range. Tunability for a given dye solution is typically limited to about 30 nm. Dye molecules photodegrade when pumped with u.v. sources. Hence, there are no known tunable dye lasers or lasers of any kind that are tunable and operated in the deep u.v. or v.u.v. spectral range.
It would therefore be desireable to have a laser that would be more broadly tunable than existing dye lasers, that would extend the spectral range of existing lasers in particular to the u.v. and v.u.v. range and that would not degrade by the pump source.